OAKLAND -- Police are seeking a man who abducted an 18-year-old woman from an East Oakland street and then drove her to the Oakland hills, where she was sexually assaulted at knifepoint before she was able to escape.

The woman was walking in the 5900 block of International Boulevard about 4:30 p.m. Tuesday when she accepted the offer of a ride from the man, police said.

The man drove her to the 4400 block of Mountain Boulevard, where he where he sexually assaulted her at knifepoint, according to police. The woman was able to escape from the car in her underwear about 6 p.m. and flagged down a motorist for help.

The suspect was described a Hispanic man in mid 20s, about 5 feet 11 inches tall, 150 pounds with short, dark spiky hair and a thin mustache. He was driving a blue older-model Cadillac or Oldsmobile, police said.

Police and Crime Stoppers of Oakland are offering up to $2,500 in reward money for information leading to the arrest of the suspect. Anyone with information may call police at 510238-3641 or a tip line at 510-637-0298. Tips can also be sent anonymously via text message. Text to 888-777 and include the words TipOaklandPD.